Generally, an oil pan is provided in a lower portion of an engine and functions as a storage section for lubricating oil that is supplied to various sections of the engine for lubrication.
For an engine having a lower case, the lower case is attached under a cylinder block, and the oil pan is attached to a lower portion of the lower case.
Some types of engines based on the conventional technology have a configuration in which a lower case having a pair of side walls and a bearing cap section for connection between the two side walls is attached to a lower portion of a cylinder block. Further, a balancer device having a balancer shaft is attached to the bearing cap section.
In this configuration, the bearing cap section vibrates in the longitudinal direction of a crank shaft in association with vibration of the balancer device in the longitudinal direction of a cylinder when the engine is driven. The vibrations of the bearing cap section are delivered to side walls of a lower case connected to the bearing cap or side walls of an oil pan joined to a lower end portion of the lower case to disadvantageously cause an increase of engine noise.
On the other hand, it is generally known, as disclosed in Japanese utility Model Registration Laid-Open Publication No. SHO 62-43161, that a rib for suppression of vibrations or noises is provided in the oil pan.
However, the conventional type of rib has the disadvantage that the rib can not sufficiently suppress vibrations delivered from a balancer device to a lower case.
When a rib is formed on an external side face of the oil pan, it is possible to suppress vibrations and noises. Provision of a rib on an external side face of the oil pan, however, disadvantageously leads to increase of size and/or weight of the oil pan, which makes it impossible to provide engine components around the oil pan.
An object of the present invention is to efficiently reduce noises generated by an engine with a balancer device attached to a bearing cap section.